Re: [PATCH v2 12/59] dyndbg, module: make proper substructs in _ddebug_info

[Louis Chauvet <louis.chauvet@bootlin.com>]

Le 20/03/2025 à 19:51, Jim Cromie a écrit :
> recompose struct _ddebug_info, inserting proper sub-structs.
> 
> The struct currently has 2 pairs of fields: descs, num_descs and
> classes, num_classes.  Several for-loops operate on these field pairs,
> soon many more will be added.
> 
> Looping over these blocks by respective field-pairs is repetitive and
> fiddly, differing only by the field-names.  Before adding a 3rd
> section and compounding the fiddly details problem, make proper
> substructs of each section, with the same named fields.
> 
> So this patch does:
> 
> Adds 3 "vector<T>" structs, each with { <T> *start, int len; }
> components, for _ddebug_descriptors, _ddebug_class_maps, and
> _ddebug_class_users respectively.
> 
> Invariant: These vectors ref a contiguous subrange of __section memory
> in builtin/DATA or in loadable modules via mod->dyndbg_info; with
> guaranteed life-time for us.
> 
> Bundles these 3 vectors (subrange-refs) struct (reformed) _ddebug_info,
> where they're __packed to close the paholes introduced otherwise.
> 
> The common fields allow improving the for_subvec() macro by dropping
> the ugly num_##<T> paste-up.
> 
> Also recompose struct ddebug_table to contain a _ddebug_info.  This
> reinforces its use as a cursor into relevant data for a builtin
> module, and access to the full _ddebug state for modules.
> 
> NOTES:
> 
> Fixup names: section names improved, struct names normalized to
> _ddebug_*

Maybe this should be in a separate patch?

> struct module contains a _ddebug_info field and module/main.c sets it
> up, so that gets adjusted.
  >
> The __packed attribute on _ddebug_info and the 3 contained structs
> closes the holes otherwise created by the structification (which was
> my excuse for not doing it originally).
> 
> Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
> ---
> -v2 rework towards front of series
> ---
>   include/asm-generic/vmlinux.lds.h |  4 +-
>   include/linux/dynamic_debug.h     | 28 +++++++---
>   kernel/module/main.c              | 12 ++--
>   lib/dynamic_debug.c               | 91 ++++++++++++++++---------------
>   4 files changed, 74 insertions(+), 61 deletions(-)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index c9c66089ea2f..f834ad1fb8c4 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -366,8 +366,8 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
>   	*(__tracepoints)						\
>   	/* implement dynamic printk debug */				\
>   	. = ALIGN(8);							\
> -	BOUNDED_SECTION_BY(__dyndbg_classes, ___dyndbg_classes)		\
> -	BOUNDED_SECTION_BY(__dyndbg, ___dyndbg)				\
> +	BOUNDED_SECTION_BY(__dyndbg_class_maps, ___dyndbg_class_maps)	\
> +	BOUNDED_SECTION_BY(__dyndbg_descriptors, ___dyndbg_descs)	\
>   	CODETAG_SECTIONS()						\
>   	LIKELY_PROFILE()		       				\
>   	BRANCH_PROFILE()						\
> diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
> index e458d4b838ac..c388ab05a6e1 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -110,13 +110,23 @@ struct ddebug_class_map {
>   		.class_names = _var##_classnames,			\
>   	}
>   
> -/* encapsulate linker provided built-in (or module) dyndbg data */
> +/*
> + * @_ddebug_info: gathers module/builtin dyndbg_* __sections together.
> + * For builtins, it is used as a cursor, with the inner structs
> + * marking sub-vectors of the builtin __sections in DATA.
> + */
> +struct _ddebug_descs {
> +	struct _ddebug *start;
> +	int len;
> +} __packed;
> +struct _ddebug_class_maps {
> +	struct ddebug_class_map *start;
> +	int len;
> +} __packed;
>   struct _ddebug_info {
> -	struct _ddebug *descs;
> -	struct ddebug_class_map *classes;
> -	unsigned int num_descs;
> -	unsigned int num_classes;
> -};
> +	struct _ddebug_descs descs;
> +	struct _ddebug_class_maps maps;
> +} __packed;
>   
>   struct ddebug_class_param {
>   	union {
> @@ -159,7 +169,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
>   
>   #define DEFINE_DYNAMIC_DEBUG_METADATA_CLS(name, cls, fmt)	\
>   	static struct _ddebug  __aligned(8)			\
> -	__section("__dyndbg") name = {				\
> +	__section("__dyndbg_descriptors") name = {		\
>   		.modname = KBUILD_MODNAME,			\
>   		.function = __func__,				\
>   		.filename = __FILE__,				\
> @@ -242,7 +252,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
>    * macro.
>    */
>   #define _dynamic_func_call_cls(cls, fmt, func, ...)			\
> -	__dynamic_func_call_cls(__UNIQUE_ID(ddebug), cls, fmt, func, ##__VA_ARGS__)
> +	__dynamic_func_call_cls(__UNIQUE_ID(_ddebug), cls, fmt, func, ##__VA_ARGS__)
>   #define _dynamic_func_call(fmt, func, ...)				\
>   	_dynamic_func_call_cls(_DPRINTK_CLASS_DFLT, fmt, func, ##__VA_ARGS__)
>   
> @@ -252,7 +262,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor,
>    * with precisely the macro's varargs.
>    */
>   #define _dynamic_func_call_cls_no_desc(cls, fmt, func, ...)		\
> -	__dynamic_func_call_cls_no_desc(__UNIQUE_ID(ddebug), cls, fmt,	\
> +	__dynamic_func_call_cls_no_desc(__UNIQUE_ID(_ddebug), cls, fmt,	\
>   					func, ##__VA_ARGS__)
>   #define _dynamic_func_call_no_desc(fmt, func, ...)			\
>   	_dynamic_func_call_cls_no_desc(_DPRINTK_CLASS_DFLT, fmt,	\
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 1fb9ad289a6f..b60f728e36ac 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -2621,12 +2621,12 @@ static int find_module_sections(struct module *mod, struct load_info *info)
>   		pr_warn("%s: Ignoring obsolete parameters\n", mod->name);
>   
>   #ifdef CONFIG_DYNAMIC_DEBUG_CORE
> -	mod->dyndbg_info.descs = section_objs(info, "__dyndbg",
> -					      sizeof(*mod->dyndbg_info.descs),
> -					      &mod->dyndbg_info.num_descs);
> -	mod->dyndbg_info.classes = section_objs(info, "__dyndbg_classes",
> -						sizeof(*mod->dyndbg_info.classes),
> -						&mod->dyndbg_info.num_classes);
> +	mod->dyndbg_info.descs.start = section_objs(info, "__dyndbg_descriptors",
> +						    sizeof(*mod->dyndbg_info.descs.start),
> +						    &mod->dyndbg_info.descs.len);
> +	mod->dyndbg_info.maps.start = section_objs(info, "__dyndbg_class_maps",
> +						   sizeof(*mod->dyndbg_info.maps.start),
> +						   &mod->dyndbg_info.maps.len);
>   #endif
>   
>   	return 0;
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index 94f6c8fd787b..663c125006d0 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -39,17 +39,15 @@
>   
>   #include <rdma/ib_verbs.h>
>   
> -extern struct _ddebug __start___dyndbg[];
> -extern struct _ddebug __stop___dyndbg[];
> -extern struct ddebug_class_map __start___dyndbg_classes[];
> -extern struct ddebug_class_map __stop___dyndbg_classes[];
> +extern struct _ddebug __start___dyndbg_descs[];
> +extern struct _ddebug __stop___dyndbg_descs[];
> +extern struct ddebug_class_map __start___dyndbg_class_maps[];
> +extern struct ddebug_class_map __stop___dyndbg_class_maps[];
>   
>   struct ddebug_table {
>   	struct list_head link;
>   	const char *mod_name;
> -	struct _ddebug *ddebugs;
> -	struct ddebug_class_map *classes;
> -	unsigned int num_ddebugs, num_classes;
> +	struct _ddebug_info info;
>   };
>   
>   struct ddebug_query {
> @@ -128,7 +126,6 @@ do {								\
>   #define v3pr_info(fmt, ...)	vnpr_info(3, fmt, ##__VA_ARGS__)
>   #define v4pr_info(fmt, ...)	vnpr_info(4, fmt, ##__VA_ARGS__)
>   
> -
>   /*
>    * simplify a repeated for-loop pattern walking N steps in a T _vec
>    * member inside a struct _box.  It expects int i and T *_sp to be
> @@ -139,8 +136,8 @@ do {								\
>    * @_vec: name of a sub-struct member in _box, with array-ref and length
>    */
>   #define for_subvec(_i, _sp, _box, _vec)				       \
> -	for ((_i) = 0, (_sp) = (_box)->_vec;			       \
> -	     (_i) < (_box)->num_##_vec;				       \
> +	for ((_i) = 0, (_sp) = (_box)->_vec.start;		       \
> +	     (_i) < (_box)->_vec.len;				       \
>   	     (_i)++, (_sp)++)
>   
>   static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
> @@ -163,6 +160,13 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
>   		  query->first_lineno, query->last_lineno, query->class_string);
>   }
>   
> +#define vpr_dt_info(dt_p, msg_p, ...) ({				\
> +	struct ddebug_table const *_dt = dt_p;				\
> +	v2pr_info(msg_p " module:%s nd:%d nc:%d nu:%d\n", ##__VA_ARGS__, \
> +		  _dt->mod_name, _dt->info.descs.len, _dt->info.maps.len, \
> +		  _dt->info.users.len);					\
> +	})
> +

This macro is not used before PATCH 17/59, maybe move it there?

By curiosity, do you know why the `verbose` parameter was introduced? It 
is not possible to use dyndbg on dyndbg?

>   #define __outvar /* filled by callee */
>   static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table const *dt,
>   							const char *class_string,
> @@ -171,7 +175,7 @@ static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table cons
>   	struct ddebug_class_map *map;
>   	int i, idx;
>   
> -	for_subvec(i, map, dt, classes) {
> +	for_subvec(i, map, &dt->info, maps) {
>   		idx = match_string(map->class_names, map->length, class_string);
>   		if (idx >= 0) {
>   			*class_id = idx + map->base;
> @@ -217,8 +221,8 @@ static int ddebug_change(const struct ddebug_query *query,
>   			valid_class = _DPRINTK_CLASS_DFLT;
>   		}
>   
> -		for (i = 0; i < dt->num_ddebugs; i++) {
> -			struct _ddebug *dp = &dt->ddebugs[i];
> +		for (i = 0; i < dt->info.descs.len; i++) {
> +			struct _ddebug *dp = &dt->info.descs.start[i];
>   
>   			/* match site against query-class */
>   			if (dp->class_id != valid_class)
> @@ -1065,8 +1069,8 @@ static struct _ddebug *ddebug_iter_first(struct ddebug_iter *iter)
>   	}
>   	iter->table = list_entry(ddebug_tables.next,
>   				 struct ddebug_table, link);
> -	iter->idx = iter->table->num_ddebugs;
> -	return &iter->table->ddebugs[--iter->idx];
> +	iter->idx = iter->table->info.descs.len;
> +	return &iter->table->info.descs.start[--iter->idx];
>   }
>   
>   /*
> @@ -1087,10 +1091,10 @@ static struct _ddebug *ddebug_iter_next(struct ddebug_iter *iter)
>   		}
>   		iter->table = list_entry(iter->table->link.next,
>   					 struct ddebug_table, link);
> -		iter->idx = iter->table->num_ddebugs;
> +		iter->idx = iter->table->info.descs.len;
>   		--iter->idx;
>   	}
> -	return &iter->table->ddebugs[iter->idx];
> +	return &iter->table->info.descs.start[iter->idx];
>   }
>   
>   /*
> @@ -1137,12 +1141,12 @@ static void *ddebug_proc_next(struct seq_file *m, void *p, loff_t *pos)
>   #define class_in_range(class_id, map)					\
>   	(class_id >= map->base && class_id < map->base + map->length)
>   
> -static const char *ddebug_class_name(struct ddebug_iter *iter, struct _ddebug *dp)
> +static const char *ddebug_class_name(struct ddebug_table *dt, struct _ddebug *dp)
>   {
> -	struct ddebug_class_map *map = iter->table->classes;
> -	int i, nc = iter->table->num_classes;
> +	struct ddebug_class_map *map;
> +	int i;
>   
> -	for (i = 0; i < nc; i++, map++)
> +	for_subvec(i, map, &dt->info, maps)

This change can't be done in 11/59? (perhaps with classes and not maps).

>   		if (class_in_range(dp->class_id, map))
>   			return map->class_names[dp->class_id - map->base];
>   
> @@ -1176,7 +1180,7 @@ static int ddebug_proc_show(struct seq_file *m, void *p)
>   	seq_putc(m, '"');
>   
>   	if (dp->class_id != _DPRINTK_CLASS_DFLT) {
> -		class = ddebug_class_name(iter, dp);
> +		class = ddebug_class_name(iter->table, dp);
>   		if (class)
>   			seq_printf(m, " class:%s", class);
>   		else
> @@ -1236,18 +1240,18 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug
>   	 * the builtin/modular classmap vector/section.  Save the start
>   	 * and length of the subrange at its edges.
>   	 */
> -	for_subvec(i, cm, di, classes) {
> +	for_subvec(i, cm, di, maps) {
>   		if (!strcmp(cm->mod_name, dt->mod_name)) {
>   			if (!nc) {
>   				v2pr_info("start subrange, class[%d]: module:%s base:%d len:%d ty:%d\n",
>   					  i, cm->mod_name, cm->base, cm->length, cm->map_type);
> -				dt->classes = cm;
> +				dt->info.maps.start = cm;
>   			}
>   			nc++;
>   		}
>   	}
>   	if (nc) {
> -		dt->num_classes = nc;
> +		dt->info.maps.len = nc;
>   		vpr_info("module:%s attached %d classes\n", dt->mod_name, nc);
>   	}
>   }
> @@ -1260,10 +1264,10 @@ static int ddebug_add_module(struct _ddebug_info *di, const char *modname)
>   {
>   	struct ddebug_table *dt;
>   
> -	if (!di->num_descs)
> +	if (!di->descs.len)
>   		return 0;
>   
> -	v3pr_info("add-module: %s %d sites\n", modname, di->num_descs);
> +	v3pr_info("add-module: %s %d sites\n", modname, di->descs.len);
>   
>   	dt = kzalloc(sizeof(*dt), GFP_KERNEL);
>   	if (dt == NULL) {
> @@ -1277,19 +1281,18 @@ static int ddebug_add_module(struct _ddebug_info *di, const char *modname)
>   	 * this struct ddebug_table.
>   	 */
>   	dt->mod_name = modname;
> -	dt->ddebugs = di->descs;
> -	dt->num_ddebugs = di->num_descs;
> +	dt->info = *di;
>   
>   	INIT_LIST_HEAD(&dt->link);
>   
> -	if (di->classes && di->num_classes)
> +	if (di->maps.len)
>   		ddebug_attach_module_classes(dt, di);
>   
>   	mutex_lock(&ddebug_lock);
>   	list_add_tail(&dt->link, &ddebug_tables);
>   	mutex_unlock(&ddebug_lock);
>   
> -	vpr_info("%3u debug prints in module %s\n", di->num_descs, modname);
> +	vpr_info("%3u debug prints in module %s\n", di->descs.len, modname);
>   	return 0;
>   }
>   
> @@ -1436,10 +1439,10 @@ static int __init dynamic_debug_init(void)
>   	char *cmdline;
>   
>   	struct _ddebug_info di = {
> -		.descs = __start___dyndbg,
> -		.classes = __start___dyndbg_classes,
> -		.num_descs = __stop___dyndbg - __start___dyndbg,
> -		.num_classes = __stop___dyndbg_classes - __start___dyndbg_classes,
> +		.descs.start = __start___dyndbg_descs,
> +		.maps.start  = __start___dyndbg_class_maps,
> +		.descs.len = __stop___dyndbg_descs - __start___dyndbg_descs,
> +		.maps.len  = __stop___dyndbg_class_maps - __start___dyndbg_class_maps,
>   	};
>   
>   #ifdef CONFIG_MODULES
> @@ -1450,7 +1453,7 @@ static int __init dynamic_debug_init(void)
>   	}
>   #endif /* CONFIG_MODULES */
>   
> -	if (&__start___dyndbg == &__stop___dyndbg) {
> +	if (&__start___dyndbg_descs == &__stop___dyndbg_descs) {
>   		if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) {
>   			pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
>   			return 1;
> @@ -1460,16 +1463,16 @@ static int __init dynamic_debug_init(void)
>   		return 0;
>   	}
>   
> -	iter = iter_mod_start = __start___dyndbg;
> +	iter = iter_mod_start = __start___dyndbg_descs;
>   	modname = iter->modname;
>   	i = mod_sites = mod_ct = 0;
>   
> -	for (; iter < __stop___dyndbg; iter++, i++, mod_sites++) {
> +	for (; iter < __stop___dyndbg_descs; iter++, i++, mod_sites++) {
>   
>   		if (strcmp(modname, iter->modname)) {
>   			mod_ct++;
> -			di.num_descs = mod_sites;
> -			di.descs = iter_mod_start;
> +			di.descs.len = mod_sites;
> +			di.descs.start = iter_mod_start;
>   			ret = ddebug_add_module(&di, modname);
>   			if (ret)
>   				goto out_err;
> @@ -1479,8 +1482,8 @@ static int __init dynamic_debug_init(void)
>   			iter_mod_start = iter;
>   		}
>   	}
> -	di.num_descs = mod_sites;
> -	di.descs = iter_mod_start;
> +	di.descs.len = mod_sites;
> +	di.descs.start = iter_mod_start;
>   	ret = ddebug_add_module(&di, modname);
>   	if (ret)
>   		goto out_err;
> @@ -1490,8 +1493,8 @@ static int __init dynamic_debug_init(void)
>   		 i, mod_ct, (int)((mod_ct * sizeof(struct ddebug_table)) >> 10),
>   		 (int)((i * sizeof(struct _ddebug)) >> 10));
>   
> -	if (di.num_classes)
> -		v2pr_info("  %d builtin ddebug class-maps\n", di.num_classes);
> +	if (di.maps.len)
> +		v2pr_info("  %d builtin ddebug class-maps\n", di.maps.len);
>   
>   	/* now that ddebug tables are loaded, process all boot args
>   	 * again to find and activate queries given in dyndbg params.

-- 
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com